Astronomers discover a super-Earth and a sub-Neptune 250 light years away from our solar system.
These planets offer a glimpse into planetary types missing from our own solar system but common in the galaxy. Using NASA’s TESS and HARPS-N, researchers measured their orbits, masses, and densities, revealing intriguing details about their compositions. TOI-1453 c’s lightweight nature hints at a thick atmosphere or a water-dominated interior, making it an exciting candidate for future atmospheric studies.
Two Mysterious Worlds Discovered
Astronomers have discovered two exoplanets orbiting TOI-1453, a star located about 250 light-years away. These planets, a super-Earth and a sub-Neptune, are among the most common types found in the galaxy, yet they are absent from our own solar system. The discovery, recently published in Astronomy & Astrophysics, opens new opportunities for studying planetary atmospheres and understanding how these worlds form and evolve.
TOI-1453 is part of a binary star system in the Draco constellation and is slightly smaller and cooler than the Sun. The two newly identified planets orbiting this star offer an intriguing look at planetary diversity. While super-Earths and sub-Neptunes dominate exoplanet populations, they remain a mystery in terms of composition and atmospheric properties. This finding provides valuable insights into the formation and development of planetary systems beyond our own.
Cutting-Edge Detection Methods
Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the HARPS-N high-resolution spectrograph, researchers confirmed the existence of TOI-1453 b and TOI-1453 c.
“The two planets present an interesting contrast in their characteristics,” explains Manu Stalport, astrophysicist at ULiège. TOI-1453 b is a super-Earth, slightly larger than our planet, and probably rocky. It completes its orbit in just 4.3 days, making it a very close planet to its star. In contrast, TOI-1453 c is a sub-Neptune, about 2.2 times the size of Earth but with an extraordinarily low mass of just 2.9 Earth masses. This makes it one of the least dense sub-Neptunes ever discovered, which raises questions about its composition.”
Transit and Radial Velocity
Detecting exoplanets remains a complex task. The team relied on two key methods to confirm their discoveries. The transit method (TESS data) measures the size and orbital period as the planet passes in front of its host star, causing a slight decrease in brightness. The second method used is radial velocity measurement (HARPS-N data), which involves observing the variations in the velocity of a star under the effect of the gravity of a planet orbiting it. By studying the gravitational influence exerted by the planets on their host star, the researchers were able to measure their masses and densities.
A Planet Unlike Any Other
“All these observations have revealed that TOI-1453 c is extremely light for its size, suggesting that it could have a thick hydrogen-rich atmosphere or a composition dominated by water. This makes it an ideal candidate for future atmospheric studies,” enthuses Manu Stalport. Understanding their formation and evolution could provide clues about the development of planetary systems, including our own.”
What’s more, the two planets orbit in a configuration close to a 3:2 resonance, meaning that for every three orbits of the inner planet, the outer planet completes almost exactly two. Such resonances are considered a natural consequence of orbital migration, offering clues as to how the planets move and settle into their final orbits.
A Future Window Into Alien Worlds
This discovery opens up new research prospects. Observational instruments such as the James Webb Space Telescope (JWST) could analyze TOI-1453 c’s atmosphere to determine its main composition. If this planet has a substantial hydrogen-rich atmosphere or a water-dominated interior, it could redefine our understanding of sub-Neptunes and their formation.
Reference: “TESS and HARPS-N unveil two planets transiting TOI-1453. A super-Earth and one of the lowest mass sub-Neptunes” by M. Stalport, A. Mortier, M. Cretignier, J.A. Egger, L. Malavolta, D.W. Latham, K.A. Collins, C.N. Watkins, F. Murgas, L.A. Buchhave, M. López-Morales, S. Udry, S.N. Quinn, A.M. Silva, G. Andreuzzi, D. Baker, W. Boschin, D.R. Ciardi, M. Damasso, L. Di Fabrizio, X. Dumusque, A. Fukui, R. Haywood, S.B. Howell, J.M. Jenkins, A. Leleu, P. Lewin, J. Lillo-Box, A.F. Martínez Fiorenzano, N. Narita, M. Pedani, M. Pinamonti, E. Poretti, R.P. Schwarz, S. Seager, A. Sozzetti, E.B. Ting, A. Vanderburg, J.N. Winn and C. Ziegler, 10 March 2025, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202452969
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3 Comments
As if they know what others are made of.
More or less, when they now if there is a lack of atmosphere or not, see the diagram. There are degeneracies, but that means some mass-radius ranges have two different solutions – it is not a complete mess, if that is what you wanted to suggest.
Not surprising, though. The planet composition, with or without atmosphere, is known to be a degenarate problem – having several solutions with the same mass-radius results.